Northwestern Polytechnical University is a National Key University, directed by the Ministry of Industry and Information Technology of the People's Republic of China, located in Xi'an, Shaanxi, China. The university emphasizes on the education and research in aeronautical, astronautical and marine engineering. In February 2012, NPU has 13,736 graduate students and 14,395 undergraduate students. Wikipedia.
Agency: Cordis | Branch: FP7 | Program: CP-FP | Phase: SPA.2011.3.2-02 | Award Amount: 11.78M | Year: 2011
The QB50 Project will demonstrate the possibility of launching a network of 50 CubeSats built by CubeSat teams from all over the world to perform first-class science and in-orbit demonstration in the largely unexplored middle and lower thermosphere. Space agencies are not pursuing a multi-spacecraft network for in-situ measurements in the middle and lower thermosphere because the cost of a network of 50 satellites built to industrial standards would be very high and not justifiable in view of the limited orbital lifetime. No atmospheric network mission for in-situ measurements has been carried out in the past or is planned for the future. A network of satellites for in-situ measurements in the middle and lower thermosphere can only be realised by using very low-cost satellites, and CubeSats are the only realistic option. The Project will demonstrate the sustained availability of a low-cost launch opportunities, for launching small payloads into low-Earth orbit; these could be microsatellites or networks of CubeSats or nanosats or many individual small satellites for scientific, technological, microgravity or biology research. The Project will include the development of a deployment system for the deployment into orbit of a large number of single, double or triple CubeSats. Once the system is developed for QB50 it can be easily adapted to other missions. QB50 will also provide a launch opportunity for key technology demonstration on IOD CubeSats such as formation flying and aerobrakes. All 50 CubeSats will be launched together into a circular orbit at approximately 380 km altitude. Due to atmospheric drag, the orbits of the CubeSats will decay and progressively lower and lower layers of the thermosphere will be explored without the need for on-board propulsion, perhaps down to 200 km. QB50 will be among the first CubeSat networks in orbit.
Xie K.,Northwestern Polytechnical University |
Wei B.,Northwestern Polytechnical University |
Wei B.,University of Delaware
Advanced Materials | Year: 2014
Stretchable energy storage and conversion devices (ESCDs) are attracting intensive attention due to their promising and potential applications in realistic consumer products, ranging from portable electronics, bio-integrated devices, space satellites, and electric vehicles to buildings with arbitrarily shaped surfaces. Material synthesis and structural design are core in the development of highly stretchable supercapacitors, batteries, and solar cells for practical applications. This review provides a brief summary of research development on the stretchable ESCDs in the past decade, from structural design strategies to novel materials synthesis. The focuses are on the fundamental insights of mechanical characteristics of materials and structures on the performance of the stretchable ESCDs, as well as challenges for their practical applications. Finally, some of the important directions in the areas of material synthesis and structural design facing the stretchable ESCDs are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Liu H.,Northwestern Polytechnical University |
Rodriguez R.M.,University of Jaén
Information Sciences | Year: 2014
Decision making is a process common to human beings. The uncertainty and fuzziness of problems demand the use of the fuzzy linguistic approach to model qualitative aspects of problems related to decision. The recent proposal of hesitant fuzzy linguistic term sets supports the elicitation of comparative linguistic expressions in hesitant situations when experts hesitate among different linguistic terms to provide their assessments. The use of linguistic intervals whose results lose their initial fuzzy representation was introduced to facilitate the computing processes in which such expressions are used. The aim of this paper is to present a new representation of the hesitant fuzzy linguistic term sets by means of a fuzzy envelope to carry out the computing with words processes. This new fuzzy envelope can be directly applied to fuzzy multicriteria decision making models. An illustrative example of its application to a supplier selection problem through the use of fuzzy TOPSIS is presented. © 2013 Elsevier Inc. All rights reserved.
Zhao X.,Northwestern Polytechnical University
Journal of Materials Chemistry | Year: 2012
The bottom-up fabrication of facile, lower-cost, larger areas optical metamaterials (OMMs) is expected to provide important benefits for applications in stealth technology and communication networks. Currently available OMMs at optical wavelengths are all composed of periodic structures, and fabricated by top-down approaches of e-beam lithography or focused ion beam technique. Limited by the high cost and extremely small sample volumes size, the fabrication of visible OMMs is still quite challenging on the nanometer scale. The rapid maturation of synthetic methodology in the field of the nanometer scale has lead to the creation of new materials at an incredible rate. In this review, we regard a V-shaped core as an artificial atom and a dendritic cell as an artificial molecule, and address the bottom-up fabrication and performance of optical metamaterials, and with an outlook toward developing devices capable of operating in optical media. © 2012 The Royal Society of Chemistry.
Deng Y.,Northwestern Polytechnical University
Applied Intelligence | Year: 2015
Dempster-Shafer evidence theory is an efficient tool in knowledge reasoning and decision-making under uncertain environments. Conflict management is an open issue in Dempster-Shafer evidence theory. In past decades, a large amount of research has been conducted on this issue. In this paper, we propose a new theory called generalized evidence theory (GET). In comparison with classical evidence theory, GET addresses conflict management in an open world, where the frame of discernment is incomplete because of uncertainty and incomplete knowledge. Within the presented GET, we define a novel concept called generalized basic probability assignment (GBPA) to model uncertain information, and provide a generalized combination rule (GCR) for the combination of GBPAs, and build a generalized conflict model to measure conflict among evidences. Conflicting evidence can be effectively handled using the GET framework. We present many numerical examples that demonstrate that the proposed GET can explain and deal with conflicting evidence more reasonably than existing methods. © 2015, Springer Science+Business Media New York.
Fan X.G.,Northwestern Polytechnical University |
Yang H.,Northwestern Polytechnical University
International Journal of Plasticity | Year: 2011
An internal-state-variable based self-consistent constitutive model was proposed for unified prediction of flow stress and microstructure evolution during hot working of wrought two-phase titanium alloys in both single-beta region and two-phase region. For each constituent phase of titanium alloys, a set of constitutive equations incorporating solution strengthening, Hall-Petch effect, dislocation interaction, and dynamic recrystallization were developed using internal state variable method. The effect of second phase on recystallization was modeled by considering particle stimulated nucleation and exerting drag force on boundary migration. The constitutive equations of constituent phases were implemented into a viscoplastic self-consistent scheme to predict the overall response of the aggregate. Predictions of the model are in good agreement with experimental results of the Ti-6Al-4V alloy and IMI834 alloy. The model can reproduce many features of the hot working of two-phase titanium alloys, including the dependence of flow stress on temperature, strain rate and alloying elements; the increase of strain rate sensitivity with temperature; the stress and strain partitionings between alpha and beta phases; the relatively high apparent activation energy in two-phase region, the decrease of recrystallization kinetics with temperature in two-phase region; and the decrease of recrystallized grain size with Zener-Hollomon parameter in beta working.
Xu B.,Northwestern Polytechnical University
Nonlinear Dynamics | Year: 2015
This paper presents adaptive dynamic surface control for the flexible model of hypersonic flight vehicle in the presence of unknown dynamics and input nonlinearity. By modeling the flexible coupling as disturbance of rigid body, based on the functional decomposition, the dynamics is divided into attitude subsystem and velocity subsystem. Flight path angle, pitch angle, and pitching rate are involved in the attitude subsystem. To eliminate the inherent problem of “explosion of complexity” in back-stepping, the dynamic surface control is investigated to construct the controller. Furthermore, direct neural control with robust design is proposed without estimating the control gain function and in this way the singularity problem could be avoided. In the last step of dynamic surface design, through the use of Nussbaum-type function, stable adaptive control is presented for the unknown dynamics with time- varying control gain function. The uniform ultimate boundedness stability of the closed-loop system is guaranteed. Simulation result shows the feasibility of the proposed method. © 2015, Springer Science+Business Media Dordrecht.
Northwestern Polytechnical University | Date: 2012-09-28
The present invention relates to a tail for improving anti-bird strike performance of an aircraft. A leading edge reinforcement having a shape of an isosceles triangle is located inside a tail leading edge. The leading edge reinforcement is spanwisely fixed in sections between respective spans formed by the wing rib inside the tail leading edge along the tail of the aircraft. An apex angle of the leading edge reinforcement is the same as an apex angle or arc transition of the tail leading edge skin. The leading edge reinforcement is fixedly connected with the small front beam by a leading edge reinforcement fixed surface. The present invention additionally installs a leading edge reinforcement in the original tail of the aircraft.
Northwestern Polytechnical University | Date: 2012-12-04
A differential microphone array (DMA) is provided that includes a number (M) of microphone sensors for converting a sound to a number of electrical signals and a processor that is configured to apply linearly-constrained minimum variance filters on the electrical signals over a time window to calculate frequency responses of the electrical signals over a plurality of subbands and sum the frequency responses of the electrical signals for each subband to calculate an estimated frequency spectrum of the sound.
Northwestern Polytechnical University | Date: 2015-07-07
A system and method relate to receiving, by a processing device, a plurality of sound signals captured at a plurality of microphone sensors, wherein the plurality of sound signals are from a sound source, and wherein a number (M) of the plurality of microphone sensors is greater than three, determining a number (K) of layers for a multistage minimum variance distortionless response (MVDR) beamformer based on the number (M) of the plurality of microphone sensors, wherein the number (K) of layers is greater than one, and wherein each layer of the multistage MVDR beamformer comprises one or more mini-length MVDR beamformers, and executing the multistage MVDR beamformer to the plurality of sound signals to calculate an estimate of the sound source.